Cut-out for incandescent electric lamps



May 5, 1931. H. RAU, JR 1,803,486

CUT-OUT FUR INGANDSSOBIT ELECTRIC LAIPS Filed June 22, 1927 INVENTOR H-R A u J ATTORNEY Patented May 1931 UNITED STATES PATENT OFFICE HENRY MU,.13., 0] NEW YORK, N. Y., ASSIGNOR '10 WESTINGHOUSE LAMP COI- PANY, ACORPOBA'IIQN OF PENNSYLVANIA CUT-OUT'I'OR INGANDESGENT ELECTRIC LAMPSApplication filed June 82, 1927. Serial No. 200,560.

This invention relates to incandescent electric lamps which are operatedin series and more particularly to a lamp having means incorporatedtherewith for permittmg the bypass of current upon the failure of thefilament of the lamp.

Certain classes of incandescent electric lamps such as those employedfor Christmas tree lighting and which may be termed miniature lamps areoperated when a given number are connected in series so that thecombined voltage of the lamps equals the line voltage supplying thecurrent.

It has heretofore been found that when using a plurality of lampsconnected in series, great inconvenience would occur upon a failure ofone of the lamps owing to a broken filament or other cause, since suchfailure breaks the continuity of the circuit and the rest of the lampsare extinguished. Inasmuch as it is difiicult to determine by inspectionwhich lamp is defective, it becomes necessary in order to select whichlamp has failed, to test by trial until the defective lamp has beendiscovered. This procedure involves considerable time and inconvenienceand has heretofore caused considerable annoyance in connection with thistype of lamp.

The present invention provides a miniature lamp of the Christmas treetype in which supplemental or auxiliary means are provided to permit aflow of current upon failure of the lament or other defect which mightprevent a flow of current in the bulb, thereby, preventing the remaininglamps of the series from becoming extinguished and immediatelyindieating which lamp of the series'is defective.

Various forms of cut-out or resistance elements have been associatedwith lamps burned in series in order to accomplish the above purpose.Considerable difiiculty has, however, arisen in providing a Christmastree lamp with a cut-out since the construction of such lamp does notappear to afford any practical way of incorporating a cut-out material.In the large type of lamps, it had been proposed to provide a lamp witha resistance material surrounding the lead-in Wires extending throughthe tubular portion of the stem. Christmas tree lamps, however, areconstructed without a stem, the mount comprising a pair of lead-wireswhich support a filament, the lead wires being secured between a bulband the exhaust tube by what is known as a butt sealing operation.Furthermore, a Christmas tree lamp must be made at relatively small costand any operation which would tend to increasev the same would beobjectionable from a manufacturing standpoint.

An object of the present invention is, therefore, to provide anincandescent lamp of the Christmas tree type having incorporated thereina supplemental by-pass or cut-out element of simple construction and atrela tively low cost.

A further object of the invention is to provide an incandescent lampbase with a cut-out element which may be quickly and convenientlyinstalled, producing an article in the form of a lamp base which may beapplied to a bulb in the same manner and without changing the factorypractice of basing.

In accomplishing the above, the base portion of a miniature or Christmastree lamp is utilized to carry a substance to provide an electricalconnection between the leading-in wires of the lamp but which isnormally resistant to prevent a flow of current and which upon a failureof the filament within the lamp will, by reason of the applied excessvoltage, be converted into a conductor to permit the passage of current.

In accomplishing the above, it has been found preferable to partiallyfill the lower portion of the base of a lamp with a layer of powder suchas a partially oxidized metallic powder which may be aluminum or iron orthe like. This powder is pressed into a compact mass and surrounds atubular member or eyelet through which one of the leading-in wiresextend, or may be disposed in direct contact with a lead wire. Thepowder is arranged so as to also contact with the metallic shell or baseof the lamp to which the opposite leading-in wire is connected. Normallythe film of oxide surrounding each particle of the powder constitutes adielectrlc or resistance which prevents the flow of current between theleads while a flow of current is current from one lead to the other andconsequentlya flow of current through the remaining lamps in the series.

When each lamp of a series of lamps is provided with a cut-out of theabove character, it will be obvious that a failure of any one of thelamps will not cause a termination of the flow of current, thus, if alamp becomes extinguished due to a defect, it may readily be detectedand removed and a newlamp installed.

Other objects and advantages of the above will be obvious from thefollowing description, reference being had to the accompanying drawingin which Fig. 1 shows an incandescent lamp of the Christmas tree typewith the base portion broken away to show the cut-out element and Fig. 2is a sectional view of a base showing a modified form of the cut-outelement.

Fig. 3 is a cross sectional view on an enlarged scale of the baseportion of Fig. 1.

Although the invention may be applied to various types of incandescentlamps, the selected embodiment thereof comprisesa bulb 10, having amount 11, supported therein. This mount usually comprises a filament 12,a pair of lead-in wires 13 and 14 secured to gether by a glass bead 15.In the manufacture of this type of lamp, an exhaust tube 16 is appliedto the end of the bulb and sealed by fusion at 17, the leading-in wirespassing through thewall of the bulb at the fused portion. The bulb isthen exhausted and the exhaust tube is tipped off, thus sealing the bulbfrom the atmosphere.

A base 18 comprised of a casing or shell is then applied to the bulb andsecured thereto by a cement 19, the leading-in wire 14 being soldered tothe base at 20. The leading-in wire 14 is usually embedded in thecement, while the leading-in wire 13 extends through the lower end ofthe base and is soldered to a contact 21. The bases as commonly used,employ a glass insulator ring 22 which surrounds the contact-and thusavoids electrical connection between the same and the metallic shell ofthe base.

In the present construction, the contact 21 is provided with a tubularmember 23 extending into the base. This contact or extending member mayas a whole be termed a contactmember or the eyelet. For the purpose ofproviding for the passage of current between the leading-in wires on afailure of the filament, the lower portion of the base may be filledwith a layer of metallic powder 24. This powder surrounds and is incontact with the eyelet and also in contact with the shell of the base.If desirable, however, the eyelet 23 may be dispensed with and the leadwire 13 disposed directly in contact with the metallic powder. The leadwire may be soldered to the contact 21 which is usually in the form of adisc embedded in the insulator ring 22.

Various substances may be employed in the form of powder, for example,particles of conductive materials may be coated with a film of anon-conductive substance which serves as a dielectric, or oxidizablemetallic powders may be used such as aluminum or iron. It has been foundpreferable to employ aluminum powder, since aluminum articles acquire acoating of oxide or film w ich remains substantially uniform, therebymaking it possible to introduce a resistance element which will not varyin its resistance properties.

It has been found desirable to apply the aluminum powder in the form ofa paste, this being accomplished b mixing the powder with any suitablefluid which will quickly evaporate, such for example as alcohol. Thepowder may, however, be applied in a dry state in which case it may betamped or pressed into a comparatively solid body; and as shown in Fig.2, a disc 25 of any suitable material such as fiber or felt may bedisposed Within the base in such position as to prevent the displacementof the powder. The disc may be held from movement by any suitable means,as for example, by riveting over the upper end 26 of the eyelet.

A lamp may be constructed in accordance with the present inventionwithout any appreciable increase in cost, thus providing a lamp whichavoids the disadvantages accompanying series lamps as heretoforeconstructed and possessing the required qualities of operation andefiiciency.

Although a preferred embodiment of the invention is shown and describedherein, it is to be understood that modifications may be made thereinwithout departing from the spirit and scope of the invention as setforth in the appended claims.

What is claimed is:

1. An incandescent electric lamp comprisng a bulb, a mount having afilament disposed in said bulb and lead wires projecting from said bulb,a base including a metallic shell and a contact member insulatedtherefrom, and one of the lead wires connected with said contact-memberand the other with the shell, a material disposed in contact with saidshell and said first named wire, said material being capable of servingas a resistance during the normal operation of the lamp and as aconductor upon the failure of a flow of current through the lamp bulb.

2. An incandescent lamp comprisin a bulb, a filament within said bulb,lead wires extending from said bulb, a base, one of said Ill wires beingin contact with said base of powdered material in said base and tactwith a portion thereof and with the other leading-in wire, said materialserving as an insulator upon a flow of current through said filament andas a, conductor upon the failure of a flow of current through saidfilament. In testimony whereof, I have hereunto subscribed my name this21st day of June,

HENRY RAU, JR. 7

a. layer in con-

